Effect of cyanotoxins on the hypothalamic-pituitary-gonadal axis in male adult mouse.

Xiong X, Zhong A, Xu H - PLoS ONE (2014)

Bottom Line:
To elucidate the associated possible mechanisms, the serum levels of testosterone, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were assessed.Furthermore, the effect of MC-LR on the viability and testosterone production of Leydig cells were tested in vitro.MC-LR significantly impaired the spermatogenesis of mice possibly through the direct or indirect inhibition of GnRH synthesis at the hypothalamic level, which resulted in reduction of serum levels of LH that lead to suppression of testosterone production in the testis of mice.

Background: Microcystins LR (MC-LR) are hepatotoxic cyanotoxins that have been shown to induce reproductive toxicity, and Hypothalamic-Pituitary-Gonadal Axis (HPG) is responsible for the control of reproductive functions. However, few studies have been performed to evaluate the effects of MC-LR on HPG axis. This study aimed to investigate the MC-LR-induced toxicity in the reproductive system of mouse and focus on the HPG axis.

Methods: Adult male C57BL/6 mice were exposed to various concentrations of MC-LR (0, 3.75, 7.50, 15.00 and 30.00 µg/kg body weight per day) for 1 to 14 days, and it was found that exposure to different concentrations of MC-LR significantly disturbed sperm production in the mice testes in a dose- and time-dependent manner. To elucidate the associated possible mechanisms, the serum levels of testosterone, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were assessed. Meanwhile, PCR assays were employed to detect alterations in a series of genes involved in HPG axis, such as FSH, LH, gonadotropin-releasing hormone (GnRH) and their complement receptors. Furthermore, the effect of MC-LR on the viability and testosterone production of Leydig cells were tested in vitro.

Results: MC-LR significantly impaired the spermatogenesis of mice possibly through the direct or indirect inhibition of GnRH synthesis at the hypothalamic level, which resulted in reduction of serum levels of LH that lead to suppression of testosterone production in the testis of mice.

Conclusions: MC-LR may be a GnRH toxin that would disrupt the reproductive system of mice.

pone-0106585-g006: Effect of MC-LR on gene expression of GnRh1, Kiss-1 and Gpr54.Mice were treated with various concentrations of MC-LR (0, 3.75, 7.50, 15.00 and 30.00 µg/kg body weight per day), at the indicated time point, the Gnrh1, Kiss-1 and Gpr54 mRNA were detected with RT-PCR. RT-PCR or quantitative real-time RT-PCR. 18s rRNA was used as an internal control. Data represent means ± SEM of 6 mice. *, P<0.05; #, P<0.01; §, P<0.005 versus control group (MC-LR 0 µg/kg body weight per day).

Mentions:
To further investigate whether MC-LR affects the HPG axis, the mRNA the expression of GnRH1, Kiss-1 and Gpr54 in the hypothalamus were analyzed by RT-PCR after mice were treated with MC-LR. Kiss1 mRNA levels in the hypothalamus did not vary significantly among the different treatment groups (Fig. 6A). No significant changes were observed in the kisspeptin receptor Gpr54 mRNA expression profile in hypothalamus of the mice at any time after MC-LR treatment (Fig. 6A). However, with regard to the changes in GnRH1 mRNA levels, there was a similar trend of GnRH1 variation (Fig. 6A) to that of LHβ mRNA level (Fig. 5A). Comparing in this way, the two figures for the two mentioned variables, quantitative real-time RT-PCR assay further confirmed that administration of MC-LR significantly decreased the GnRH1 mRNA levels in a dose- and time-dependent manner as compared with the group received the vehicle control saline treatment (Fig. 6B).

pone-0106585-g006: Effect of MC-LR on gene expression of GnRh1, Kiss-1 and Gpr54.Mice were treated with various concentrations of MC-LR (0, 3.75, 7.50, 15.00 and 30.00 µg/kg body weight per day), at the indicated time point, the Gnrh1, Kiss-1 and Gpr54 mRNA were detected with RT-PCR. RT-PCR or quantitative real-time RT-PCR. 18s rRNA was used as an internal control. Data represent means ± SEM of 6 mice. *, P<0.05; #, P<0.01; §, P<0.005 versus control group (MC-LR 0 µg/kg body weight per day).

Mentions:
To further investigate whether MC-LR affects the HPG axis, the mRNA the expression of GnRH1, Kiss-1 and Gpr54 in the hypothalamus were analyzed by RT-PCR after mice were treated with MC-LR. Kiss1 mRNA levels in the hypothalamus did not vary significantly among the different treatment groups (Fig. 6A). No significant changes were observed in the kisspeptin receptor Gpr54 mRNA expression profile in hypothalamus of the mice at any time after MC-LR treatment (Fig. 6A). However, with regard to the changes in GnRH1 mRNA levels, there was a similar trend of GnRH1 variation (Fig. 6A) to that of LHβ mRNA level (Fig. 5A). Comparing in this way, the two figures for the two mentioned variables, quantitative real-time RT-PCR assay further confirmed that administration of MC-LR significantly decreased the GnRH1 mRNA levels in a dose- and time-dependent manner as compared with the group received the vehicle control saline treatment (Fig. 6B).

Bottom Line:
To elucidate the associated possible mechanisms, the serum levels of testosterone, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were assessed.Furthermore, the effect of MC-LR on the viability and testosterone production of Leydig cells were tested in vitro.MC-LR significantly impaired the spermatogenesis of mice possibly through the direct or indirect inhibition of GnRH synthesis at the hypothalamic level, which resulted in reduction of serum levels of LH that lead to suppression of testosterone production in the testis of mice.

Background: Microcystins LR (MC-LR) are hepatotoxic cyanotoxins that have been shown to induce reproductive toxicity, and Hypothalamic-Pituitary-Gonadal Axis (HPG) is responsible for the control of reproductive functions. However, few studies have been performed to evaluate the effects of MC-LR on HPG axis. This study aimed to investigate the MC-LR-induced toxicity in the reproductive system of mouse and focus on the HPG axis.

Methods: Adult male C57BL/6 mice were exposed to various concentrations of MC-LR (0, 3.75, 7.50, 15.00 and 30.00 µg/kg body weight per day) for 1 to 14 days, and it was found that exposure to different concentrations of MC-LR significantly disturbed sperm production in the mice testes in a dose- and time-dependent manner. To elucidate the associated possible mechanisms, the serum levels of testosterone, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were assessed. Meanwhile, PCR assays were employed to detect alterations in a series of genes involved in HPG axis, such as FSH, LH, gonadotropin-releasing hormone (GnRH) and their complement receptors. Furthermore, the effect of MC-LR on the viability and testosterone production of Leydig cells were tested in vitro.

Results: MC-LR significantly impaired the spermatogenesis of mice possibly through the direct or indirect inhibition of GnRH synthesis at the hypothalamic level, which resulted in reduction of serum levels of LH that lead to suppression of testosterone production in the testis of mice.

Conclusions: MC-LR may be a GnRH toxin that would disrupt the reproductive system of mice.